System for jamming wireless communications

ABSTRACT

1. In a system for jamming wireless communications with the aid of a searching receiver for ascertaining senders which are engaged in the transmission of messages, a powerful jamming transmitter for radiating jamming signals on the waves of ascertained senders, whereby said receiver and transmitter are alternately operative to ascertain transmitting senders and to transmit jamming signals, respectively, which comprises means at the searching receiver for converting received frequency signals into lower frequency ranges, means for successively converting said lower frequency range signals into a plurality of individual ranges, means forming a group of frequency-analyzing channels, means for connecting said frequency-analyzing channel means to respective outputs of said plurality of individual ranges, whereby each individual range is searched for frequencies therein by the common group of frequency-analyzing channels, means operatively connected to said frequency-analyzing channel means responsive upon ascertainment of a signal thereby, to effect jamming transmission corresponding to the received frequency of such ascertained signal.

ilnited States Deserno et al.

SYSTEM FOR JAMMluGwiRELEss COMMUNICATIONS Inventors: Peter Deserno;Friedrich Kauderer,

both of Munich; Hans Prost, Munich-Solln, all of Germany PrimaryExaminer--Benjamin A. Borchelt Assistant Examiner-H. A. BirmielAttorney-Hill, Sherman, Meroni, Gross & Simpson :REOUENCV EU3 com/{armIs 7 TRANSFORMATION STAGES EuI res (ONVHSION OSCVLLATOR 54 CONVERS/ONOSCILLATOP CONVERSION OSClLLATO" 11 3,739,233 June 12, 1973 EXEMPLARYCLAIM 1. In a system for jamming wireless communications with the aid ofa searching receiver for ascertaining senders which are engaged in thetransmission of messages, a powerful jamming transmitter for radiatingjamming signals on the waves of ascertained senders, whereby saidreceiver and transmitter are alternately operative to ascertaintransmitting senders and to transmit jamming signals, respectively,which comprises means at the searching receiver for converting receivedfrequency signals into lower frequency ranges, means for successivelyconverting said lower frequency range signals into a plurality ofindividual ranges, mans forming a group of frequency-analyzing channels,means for connecting said frequency-analyzing channel means torespective Outputs of said plurality of individual ranges, whereby eachindividual range is searched for frequencies therein by the common groupof frequency-analyzing channels, means operatively connected to saidfrequencyanalyzing channel means responsive upon ascertainment of asignal thereby, to effect jamming transmission corresponding to thereceived frequency of such ascertained signal.

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Z24- r Km 0 r mm Zs a, 4 ill as l 2 a A 5 TIMING u PULSE nul 11GENERATOR 'QQ 'ZE comnor AMPLIFIER CONVERTER SYSTEM FOR JAMMING WIRELESSCOMMUNICATIONS The invention disclosed herein is concerned with a systemfor jamming wireless communications and may be considered as animprovement on the system disclosed in copending application Ser. No.154,913, filed Sept. 18, 1961, which is owned by the assignee named inthe present case.

The system disclosed in the above indicated copending applicationcomprises a tracking or searching receiver and a powerful jammingtransmitter, for alternatively ascertaining senders which are engaged intransmitting and radiating jamming signals on the wave length of therespective ascertained senders, the track ing receiver searching withina wide wave range, in a multitude of mutually bordering narrow receivingchannels, for senders which are transmitting. Senders which are thus inone or more of these receiving channels ascertained as being engaged intransmitting, are held, and an amplified interference frequency spectrumis by the jamming transmitter in the subsequent jamming intervalradiated over the respective ascertained channels. The searching andjamming time intervals may periodically alternate in rapid succession,for example, in the order of magnitude of a few milliseconds.

The system according to the copending application entails a relativelygreat expenditure, since the supervision and jamming of a wide frequencyband requires for the frequency analysis a great number of narrowchannels and therewith a correspondingly great number of amplifiers andchannel filters.

In order to reduce this expenditure, the prior copending applicationproposes to carry out the frequency analysis in a lower frequencyposition, after one or several transformations of the receivedfrequency, and to effect at the transmitter side a reformation of thereceived frequency into the original frequency position. This may bedone by subdividing the frequency measuring range or interference range,respectively, by repeated frequency transformation, into differentintermediate frequency positions, so as to form groups of identicalchannels, for example, preliminary groups, basic groups, superiorgroups, etc., thus permitting for the respective channels the use ofstructurally similar component parts which recur repeatedly in thevarious channels. However, the expenditure required in such arrangementis still quite high.

The object of the present invention is to achieve a considerablereduction of expenditure for the frequency analysis at the receiver sideand a like reduction of expenditure for the production of the frequencyspectrum at the transmitter side.

The present invention proposes a solution for the problems involved,which is based upon a plural utilization of filter and amplifier groupsin the manner of the time-division multiplex technique. According to theinvention, the frequency range which is to be searched is, aftertransformation into a lower fixed frequency position, subdivided into aplurality of individual ranges, and such individual ranges are searchedin lower frequency position in definite sequence, with the aid of thesame groups of channels. A corresponding subdivision is effected at thetransmitter side. The searching can be effected, upon transformation tothe lower frequency position, by appropriately changing thetransformation frequency by switching-over or the like. The

advantage resides in that the same group of channels can be utilized forthe frequency analysis in each of the individual ranges, by alwaystransforming the individual ranges to this same group. This results in areduction of the number of the required channels by a factor which isequal to the number of individual ranges into which the frequency rangewhich is to be searched, is subdivided. For example, if the frequencyrange is subdivided into five individual ranges, the num ber of channelswill be reduced to one-fifth of the channels required in the arrangementaccording to the copending application.

In accordance with the invention, the broad frequency range which is tobe jammed is sub-divided at the transmitter side into correspondinginterference or jamming frequency ranges. These jamming frequency rangesat the transmitter side are subdivided into corresponding jammingchannels as at the receiver side. The jamming channels may be obtainedby frequency transformation from a channel with interference modulation,for example, from the spectrum of a noise generator. A number of jammingchannels is thereby used, which corresponds to the number of channelsoperating in lower frequency position at the group of channels at thereceiver side, such jamming channels being transformed into thecorresponding jamming frequency ranges as the individual ranges at thereceiver side.

Further features and details of the invention will appear from theappended claims and from the description which is rendered below withreference to the accompanying drawings, showing embodiments thereof.

FIG. 1 shows in block diagram manner a receiver arrangement according tothe invention;

FIG. 2 illustrates an embodiment of a cooperating transmitterarrangement;

FIG. 3 represents a timing plan for the transmitting and receivingtimes; and

FIG. 4 shows a timing plan for differently selected transmitter andreceiving intervals.

The receiver arrangement according to FIG. 1 is designed for searching afrequency range a width of 30 megacycles which extends from 220 to 250megacycles. This frequency range, in the illustrated embodiment, is 6megacycles, and is subsequently transformed in lower frequency positionto a group of 125 channels, each with 48 kilocycles band width. This isaccomplished in five transformation stages EUl EUS. The received voltageis from a receiving antenna conducted to the input terminal E andreaches the frequency converter U in the first conversion ortransformation stage EUl, in which it is transformed into a fixed firstintermediate frequency position from 60 to megacycles, suchtransformation being effected by a transformation frequency f,,. Atiming switch Z, is operative to connect the oscillator 0,, andtherewith the reception, for the duration of a searching or trackinginterval, while disconnecting the oscillator during the jammingtransmission interval.

The next conversion or transformation stage EU2 employs for the scanningor tracking of the regions a transformation arrangement which can beswitched over. This arrangement comprises a plurality of parallelconnected frequency converters U,, U,, ,'corresponding in number to thenumber of individual searching or tracking times. Said convertersinclude conversion oscillators O 0, which have respective operatingfrequencies of f .fos, which oscillators are respectively operativelyconnected and disconnected, in the rhythm of the individual searchingtimes, by means of the timing switches Z 2, The individual ranges 60-66;66-72', 72-78; 78-84 and 84-90 megacycles are by these converterssuccessively transformed to a second intermediate frequency range of10-16 megacycles, which is the same for all individual ranges, and whichis amplified in an amplifier VEU The second intermediate frequency rangeis in the third conversion or transformation stage EU3 subdivided intofive ranges of 10-1 1.2; 11.2-12.4; 12.4-13.6; 13.6-14.8 and 14.8-16megacycles and transformed into a third intermediate frequency range of1.8-3 megacycles, such subdivision being effected by five converters U,U, by conversion or transformation frequencies f,, .f from oscillators0, thus resulting in five third inter-mediate frequency groups.

Each of the five intermediate frequency groups is sub-divided, in thefourth conversion or transformation stage EUd, into five ranges of18-204; 2.04-2.28; 2.28-2.52; 2.52-2.76 and 276-130 megacycles. Theresulting 5 times 5 ranges are converted into a fourth intermediatefrequency range of 312-552 kilocycles, by 25 further frequencyconverters, of which only one converter U with a conversion oscillator0, and a conversion frequency f is shown in FIG. 1.

Each fourth intermediate frequency range is, ahead of the fifthconversion or transformation stage EUS, subdivided into five ranges of312-360; 360-408; 408-456; 456-504 and 504-552 kilocycles, thusresulting in 25 groups each with five channels each with a 48 kilocycleswidth.

These 125 channels are by means of 125 further frequency converters, ofwhich only the converter U with an oscillator 0, and a conversionfrequencyf is shown, converted to 125 channels in a fifth intermediatefrequency range of 60-108 ltilocycles. These channels are mutuallysimilar and correspond, for example, to the basic or fundamental groupsof carrier frequency communication systems.

All individual ranges of the frequency range which is to be searched aresuccessively analyzed with the aid of this common group of 125 channels,by switching over the conversion or transformation frequencies. In theabsence of the switching-over according to the invention, there would berequired 625 channels for the searching of the same frequency range.

Each of the frequency converters in the individual conversion ortransformation stages, comprises in known manner amplifiers and filtersof the indicated higher and lower frequency positions and band widths,as well as a mixingand superposing part to which is connected therespective conversion oscillator.

In the operation of the arrangement, the oscillator frequency f is byway of the timing switch Z operatively connected, for example, for asearching interval of 0.5 millisecond, and the five oscillatorfrequenciesf .f,,,, are operatively connected with the respectiveconverters, each for one-fifth of the searching interval, that is, forabout 0.1 millisecond. The frequency regions 60-66 mc; 66-72 mc; 72-78mc; 78-84 me and 84-90 mc are in this manner successively converted ortransformed to the second intermediate frequency of -16 megacycles.During the first one-fifth of the searching or tracking interval,reception of the band 60-66 megacycles is effected, for example, by

way of the converter U while the other four converters do not receiveoscillator voltage and are thus inoperative. This partial range of 60-66megacycles is after three further band subdivisions and conversionstransferred to 125 channels or fundamental groups each with 60-108kilocycles. Each of these channels or channel groups has five outputcircuits, each of which is allotted to an individual range and connectedwith the respective individual range by way of timing switches Z Z theconnections being effected in the receiving switching rhythm,simultaneously with the respective individual ranges. The outputcircuits in which transmitter frequencies are ascertained, are for theentire range held for the duration of one or more supervision intervalsor periods. A supervision interval or period is understood to cover thetime during which the entire frequency range is tracked or searched onceor jammed by the transmission ofjamming frequency. The holding orstoring of the output circuits can be effected by delay action which isin the present case brought about by impulse expanders D D which arerespectively serially connected with the timing switches Z Z Thetransmitter or sender arrangement shown in FIG. 2 comprises five sendergroups 86 $6 each group having channel switches K K Character Rindicates a noise generator and VR a control amplifier for the spectrumthereof, such spectrum being utilized to form, with the aid of 63frequency converters RU1 RU63, 125 noise channels in the range of 10-16megacycles, each with 48 kilocycles band width. Two noise channels areobtained from each frequency converter owing to the upper and lower sidebands produced upon frequency conversion or transformation of thespectrum of the noise generator R.

The channel switches K K for switching-in the channels, are in theillustrated example arranged in a crossbar distributor which is in onecoordinate direction provided with longitudinally extending barscorresponding in number to the number of individual searching ortracking times, there being in the present case five such longitudinalbars. Transverse bars are provided in the other coordinate direction,the number of such latter bars (125) corresponding to the number ofnoise channels which are connected with the outputs of the noisefrequency converters RUl RU63. The channel switches K K are combined ingroups SG $6 which correspond to the jamming frequency ranges. Theactuating windings for the channel switches of the individual sendergroups SG SG are synchronously connected, by means of the timingswitches Z Z (FIG. 1), with the corresponding five output circuits ofthe receiving channels, the channel switches being thus operativelycontrolled by the output circuits of the receiving channels. Eachjamming or interference channel can therefore be switched through, bythe respective transverse bar, to each longitudinal bar.

There are provided frequency converters SU,, SU cooperating withconversion oscillators S0,, SO for the conversion of theswitched-through jamming channels to the individual ranges which areswept over in the conversion at the receiver, such frequency convertersbeing connected to the outputs of the respective longitudinal bars ofthe crossbar distributor and the outputs thereof being interconnected asshown. These frequency converters effect, in the frequency conversionstage SU2, conversion of the five jamming frequency bands, from theirposition in the range of -16 megacycles, into the successive jammingfrequency ranges 60-66, 66-72, 7278, 78-84 and 84-90 megacycles. Theentire band of 60-90 megacycles is amplified in an amplifier VSU and isby way of the sender switch Zs connected to the sender converter SU,which is connected with the sender antenna S from which are radiated thejamming frequencies in the range from 220 to 260 megacycles. A senderconversion oscillator SO, produces the required conversion frequencyf,,. A beat or timing pulse generator T controls the operation of thetiming switches Za, Zb, Zc, Zs in the sequence indicated. A linearizedfeedback GK is branched off from the terminal stage of the sender andcarried back to the intermediate frequency part thereof, the optimumadjustment being effected by means of a phase shifter The output powerof the sender is appropriately held constant by means of an automaticamplifier control, since the switching in of the number of jammingchannels can rapidly and strongly fluctuate. An amplifier controlvoltage is for this purpose branched off at the amplifier VSU ahead ofthe sender converter SU,,, by way of a rectifier G1, acting on theregulation or control amplifier VR cooperating with the noise generatorR, whereby the output voltage is so regulated that the sender operatesalways with maximum output power irrespective of the operativeconnection and disconnection of jamming channels.

The system according to the invention can be operated so that allindividual ranges are searched once during a searching or trackinginterval, step-by-step, and thereupon transmission of jammingfrequencies is effected. Another possibility resides in transmitting jamming signals in an ascertained individual range immediately or after agiven delay, after each individual searching interval, and continuing,after each interruption caused by the next individual searchinginterval, the jamming of the previously ascertained channels.Accordingly, all individual ranges are in the first case searched beforethe switching over to jamming transmission, while jamming signals are inthe second case transmitted after the searching of each individualrange, in the channels ascertained thereby, the jamming transmissionbeing briefly interrupted so as to effect subsequent searching of theindividual ranges, and being after each interruption resumed withrespect to newly ascertained channels and also in the previouslyoperatively connected channels.

The individual ranges can be successively searched in any desiredsequence. It is, for example, possible to continuously successivelysearch mutually bordering individual ranges, by continuouslysuccessively operatively connecting rising or falling conversionfrequencies during the individual searching intervals. It is alsopossible to intermix the individual searching intervals with therespectively allotted conversion frequencies, so as to increase thedifficulties attending preventive steps taken by the jammed parties.

In accordance with the timing plan shown in FIG. 3, all individualranges are during a searching interval Te searched once, in briefindividual searching intervals Te, Te, with the conversion frequenciesf, .f whereupon the arrangement is switched over to jamming in theascertained channels, at least for ajamming transmission interval Ts.After the jamming transmission interval Ts follows the next searchinginterval Te and jamming is for some time continued in the followinginterval Ts also in one or more of the channels ascertained in thecourse of one or more previous individual searching times. The durationof the jamming transmission intervals Ts can be altered regularly orirregularly. It is not necessary to operate, as indicated in FIG. 3,with continuously rising or falling conversion frequencies; the sequenceof the searching of the ranges may be intermixed as desired.

The operation according to the timing plan shown in FIG. 4 providesafter each individual searching interval Te Te immediate jammingtransmission in the ascertained channels of the corresponding individualranges. Accordingly, there is in this case no continuous searching timein which all individual ranges are successively searched, but theindividual searching times are distributed over a supervising period. Asindicated, jamming transmission is after each interruption by the nextsuccessive individual searching interval, continued in the previouslyascertained channels. This mode of operation effects jammingtransmission in individual jamming intervals S 8, The duration of theseindividual jamming intervals, which are indicated in FIG. 4 as being ofequal length, can also be varied so as to increase the difficultiesattending preventive measures taken by the jammed parties.

The conversion frequencies f, of the terminal frequencies at the senderand receiver sides may be advantageously synchronously wobbled,preferably by the frequency from a common oscillator which is wobbledand take the place of the separate oscillators 0, and S0,. The advantageobtained thereby resides in that gaps are avoided between the channelsin the supervised frequency range.

Changes may be made within the scope and spirit of the appended claimswhich define what is believed to be new and desired to have protected byLetters Patent.

We claim:

I. In a system for jamming wireless communications with the aid of asearching receiver for ascertaining senders which are engaged in thetransmission of messages, a powerful jamming transmitter for radiatingjamming signals on the waves of ascertained senders, whereby saidreceiver and transmitter are alternately operative to ascertaintransmitting senders and to transmit jamming signals, respectively,which comprises means at the searching receiver for converting receivedfrequency signals into lower frequency ranges, means for successivelyconverting said lower frequency range signals into a plurality ofindividual ranges, means forming a group of frequency-analyzingchannels, means for connecting said frequency-analyzing channel means torespective outputs of said plurality of individual ranges, whereby eachindividual range is searched for frequencies therein by the common groupof frequency-analyzing channels, means operatively connected to saidfrequency-analyzing channel means responsive upon ascertainment of asignal thereby, to effect jamming transmission corresponding to thereceived frequency of such ascertained signal.

2. A system according to claim 1, comprising means for controlling saidfrequency converting means, said channel connecting means and saidtransmission means to effect a searching during a searching interval, instep-by-step manner, within brief individual searching timescorresponding to the switching-in instants of conversion frequencies, toascertain transmitting senders, and effecting a jamming transmissiononly after completion of the searching of all individual ranges.

3. A system according to claim 1, comprising means for transmittingcontrolling said frequency converting means said channel connectingmeans, and said transmission means to effect a transmission of jammingsignals in ascertained channels after each individual searchinginterval, transmission of jamming signals being interrupted bysubsequent searching intervals and being after such interruptionsresumed in the crresponding channels including previously ascertainedchannels 4. A system according to claim 1, wherein the channelconnecting means is so constructed that individual searching intervalsare successively effected with continuously rising conversionfrequencies.

5. A system according to claim 1, wherein the channel connecting meansis so constructed that individual searching intervals are effected withintermixed conversion frequencies.

6. A system according to claim 1, wherein each channel of said group ofchannels has a number of output circuits corresponding to the number ofindividual ranges, each output circuit being respectively allocated toan individual range and being synchronously operatively switchedtherewith.

7. A system according to claim 6, comprising impulse expander meansoperatively connected to said channelforming means for holding outputcircuits, in which sender frequencies are ascertained, for the durationof one or more supervision periods for the entire range.

8. A system according to claim 1, wherein said first mentioned frequencyconverting means comprises a plurality of parallel connected frequencyconverters, corresponding in number to the number of individualsearching times and operating with mutually different conversionfrequencies, and means for respectively operatively connecting anddisconnecting said converters in the rhythm of the individual searchingtimes.

9. A system according to claim 1, wherein said transmission means is soconstructed that the frequency range which is to be jammed is at thejamming transmitter subdivided into jamming frequency ranges withjamming channels corresponding to the same channel distribution as atthe searching receiver.

10. A system according to claim 9, comprising means for obtaining thegroup ofjamming channels at the jamming transmitter by frequencyconversion from a channel with interference modulation.

11. A system according to claim 10, wherein the jamming channels areformed by upper and lower side bands appearing incident to the frequencyconversion.

12. A system according to claim 11, comprising means for converting thegroup of jamming channels into jamming frequency ranges corresponding toindividual ranges at the receiver side.

13. A system according to claim 12, comprising channel switches foroperatively connecting the jamming channels, means for combining saidchannel switches in groups corresponding to the jamming frequencyranges, and means in the output circuits for operatively controllingsaid channel switches.

14. A system according to claim 13, wherein the conversion frequenciesat the respective receiverand transmitter terminal frequencies aresynchronously wobbled by a frequency supplied by a common oscillator.

15. A system according to claim 14, wherein the channel connecting meansis so constructed that individual search intervals are successivelyeffected with continuously falling conversion frequencies.

16. A system according to claim 13, comprising means disposed in themanner of a crossbar arrangement for disposing said channel switches.

17. A system according to claim 16, wherein said crossbar arrangement isformed by a crossbar distributor which comprises, in one coordinatedirection, longitudinal bars corresponding in number to the number ofindividual ranges, and in the other coordinate direction transverse barscorresponding in number to the number of jamming channels for therespective individual ranges, means for connecting said transverse barswith the jamming channels, said channel switches being operative forconnecting each jamming channel with each longitudinal bar.

* l l l

1. In a system for jamming wireless communications with the aid of asearching receiver for ascertaining senders which are engaged in thetransmission of messages, a powerful jamming transmitter for radiatingjamming signals on the waves of ascertained senders, whereby saidreceiver and transmitter are alternately operative to ascertaintransmitting senders and to transmit jamming signals, respectively,which comprises means at the searching receiver for converting receivedfrequency signals into lower frequency ranges, means for successivelyconverting said lower frequency range signals into a plurality ofindividual ranges, means forming a group of frequency-analyzingchannels, means for connecting said frequency-analyzing channel means torespective outputs of said plurality of individual ranges, whereby eachindividual range is searched for frequencies therein by the common groupof frequency-analyzing channels, means operatively connected to saidfrequency-analyzing channel means responsive upon ascertainment of asignal thereby, to effect jamming transmission corresponding to thereceived frequency of such ascertained signal.
 2. A system according toclaim 1, comprising means for controlling said frequency convertingmeans, said channel connecting means and said transmission means toeffect a searching during a searching interval, in step-by-step manner,within brief individual searching times corresponding to theswitching-in instants of conversion frequencies, to ascertaintransmitting senders, and effecting a jamming transmission only aftercompletion of the searching of all individual ranges.
 3. A systemaccording to claim 1, comprising means for transmitting controlling saidfrequency converting means , said channel connecting means, and saidtransmission means to effect a transmission of jamming signals inascertained channels after each individual searchIng interval,transmission of jamming signals being interrupted by subsequentsearching intervals and being after such interruptions resumed in thecorresponding channels including previously ascertained channels.
 4. Asystem according to claim 1, wherein the channel connecting means is soconstructed that individual searching intervals are successivelyeffected with continuously rising conversion frequencies.
 5. A systemaccording to claim 1, wherein the channel connecting means is soconstructed that individual searching intervals are effected withintermixed conversion frequencies.
 6. A system according to claim 1,wherein each channel of said group of channels has a number of outputcircuits corresponding to the number of individual ranges, each outputcircuit being respectively allocated to an individual range and beingsynchronously operatively switched therewith.
 7. A system according toclaim 6, comprising impulse expander means operatively connected to saidchannel-forming means for holding output circuits, in which senderfrequencies are ascertained, for the duration of one or more supervisionperiods for the entire range.
 8. A system according to claim 1, whereinsaid first mentioned frequency converting means comprises a plurality ofparallel connected frequency converters, corresponding in number to thenumber of individual searching times and operating with mutuallydifferent conversion frequencies, and means for respectively operativelyconnecting and disconnecting said converters in the rhythm of theindividual searching times.
 9. A system according to claim 1, whereinsaid transmission means is so constructed that the frequency range whichis to be jammed is at the jamming transmitter subdivided into jammingfrequency ranges with jamming channels corresponding to the same channeldistribution as at the searching receiver.
 10. A system according toclaim 9, comprising means for obtaining the group of jamming channels atthe jamming transmitter by frequency conversion from a channel withinterference modulation.
 11. A system according to claim 10, wherein thejamming channels are formed by upper and lower side bands appearingincident to the frequency conversion.
 12. A system according to claim11, comprising means for converting the group of jamming channels intojamming frequency ranges corresponding to individual ranges at thereceiver side.
 13. A system according to claim 12, comprising channelswitches for operatively connecting the jamming channels, means forcombining said channel switches in groups corresponding to the jammingfrequency ranges, and means in the output circuits for operativelycontrolling said channel switches.
 14. A system according to claim 13,wherein the conversion frequencies at the respective receiver- andtransmitter terminal frequencies are synchronously wobbled by afrequency supplied by a common oscillator.
 15. A system according toclaim 14, wherein the channel connecting means is so constructed thatindividual search intervals are successively effected with continuouslyfalling conversion frequencies.
 16. A system according to claim 13,comprising means disposed in the manner of a crossbar arrangement fordisposing said channel switches.
 17. A system according to claim 16,wherein said crossbar arrangement is formed by a crossbar distributorwhich comprises, in one coordinate direction, longitudinal barscorresponding in number to the number of individual ranges, and in theother coordinate direction transverse bars corresponding in number tothe number of jamming channels for the respective individual ranges,means for connecting said transverse bars with the jamming channels,said channel switches being operative for connecting each jammingchannel with each longitudinal bar.